lockmgr.h revision 176151
1/*- 2 * Copyright (c) 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code contains ideas from software contributed to Berkeley by 6 * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating 7 * System project at Carnegie-Mellon University. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)lock.h 8.12 (Berkeley) 5/19/95 34 * $FreeBSD: head/sys/sys/lockmgr.h 176151 2008-02-10 15:50:21Z attilio $ 35 */ 36 37#ifndef _SYS_LOCKMGR_H_ 38#define _SYS_LOCKMGR_H_ 39 40#ifdef DEBUG_LOCKS 41#include <sys/stack.h> /* XXX */ 42#endif 43#include <sys/queue.h> 44#include <sys/lock.h> 45 46struct mtx; 47 48/* 49 * The general lock structure. Provides for multiple shared locks, 50 * upgrading from shared to exclusive, and sleeping until the lock 51 * can be gained. 52 */ 53struct lock { 54 struct lock_object lk_object; /* common lock properties */ 55 struct mtx *lk_interlock; /* lock on remaining fields */ 56 u_int lk_flags; /* see below */ 57 int lk_sharecount; /* # of accepted shared locks */ 58 int lk_waitcount; /* # of processes sleeping for lock */ 59 short lk_exclusivecount; /* # of recursive exclusive locks */ 60 short lk_prio; /* priority at which to sleep */ 61 int lk_timo; /* maximum sleep time (for tsleep) */ 62 struct thread *lk_lockholder; /* thread of exclusive lock holder */ 63 struct lock *lk_newlock; /* lock taking over this lock */ 64 65#ifdef DEBUG_LOCKS 66 struct stack lk_stack; 67#endif 68}; 69 70#define lk_wmesg lk_object.lo_name 71/* 72 * Lock request types: 73 * LK_SHARED - get one of many possible shared locks. If a process 74 * holding an exclusive lock requests a shared lock, the exclusive 75 * lock(s) will be downgraded to shared locks. 76 * LK_EXCLUSIVE - stop further shared locks, when they are cleared, 77 * grant a pending upgrade if it exists, then grant an exclusive 78 * lock. Only one exclusive lock may exist at a time, except that 79 * a process holding an exclusive lock may get additional exclusive 80 * locks if it explicitly sets the LK_CANRECURSE flag in the lock 81 * request, or if the LK_CANRECUSE flag was set when the lock was 82 * initialized. 83 * LK_UPGRADE - the process must hold a shared lock that it wants to 84 * have upgraded to an exclusive lock. Other processes may get 85 * exclusive access to the resource between the time that the upgrade 86 * is requested and the time that it is granted. 87 * LK_DOWNGRADE - the process must hold an exclusive lock that it wants 88 * to have downgraded to a shared lock. If the process holds multiple 89 * (recursive) exclusive locks, they will all be downgraded to shared 90 * locks. 91 * LK_RELEASE - release one instance of a lock. 92 * LK_DRAIN - wait for all activity on the lock to end, then mark it 93 * decommissioned. This feature is used before freeing a lock that 94 * is part of a piece of memory that is about to be freed. 95 * LK_EXCLOTHER - return for lockstatus(). Used when another process 96 * holds the lock exclusively. 97 * 98 * These are flags that are passed to the lockmgr routine. 99 */ 100#define LK_TYPE_MASK 0x0000000f /* type of lock sought */ 101#define LK_SHARED 0x00000001 /* shared lock */ 102#define LK_EXCLUSIVE 0x00000002 /* exclusive lock */ 103#define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */ 104#define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */ 105#define LK_RELEASE 0x00000006 /* release any type of lock */ 106#define LK_DRAIN 0x00000007 /* wait for all lock activity to end */ 107#define LK_EXCLOTHER 0x00000008 /* other process holds lock */ 108/* 109 * External lock flags. 110 * 111 * These may be set in lock_init to set their mode permanently, 112 * or passed in as arguments to the lock manager. 113 */ 114#define LK_EXTFLG_MASK 0x00000ff0 /* mask of external flags */ 115#define LK_NOWAIT 0x00000010 /* do not sleep to await lock */ 116#define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */ 117#define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */ 118#define LK_NOSHARE 0x00000080 /* Only allow exclusive locks */ 119#define LK_TIMELOCK 0x00000100 /* use lk_timo, else no timeout */ 120#define LK_NOWITNESS 0x00000200 /* disable WITNESS */ 121#define LK_NODUP 0x00000400 /* enable duplication logging */ 122/* 123 * Nonpersistent external flags. 124 */ 125#define LK_RETRY 0x00001000 /* vn_lock: retry until locked */ 126#define LK_INTERLOCK 0x00002000 /* 127 * unlock passed mutex after getting 128 * lk_interlock 129 */ 130/* 131 * Internal lock flags. 132 * 133 * These flags are used internally to the lock manager. 134 */ 135#define LK_WANT_UPGRADE 0x00010000 /* waiting for share-to-excl upgrade */ 136#define LK_WANT_EXCL 0x00020000 /* exclusive lock sought */ 137#define LK_HAVE_EXCL 0x00040000 /* exclusive lock obtained */ 138#define LK_WAITDRAIN 0x00080000 /* process waiting for lock to drain */ 139#define LK_DRAINING 0x00100000 /* lock is being drained */ 140#define LK_INTERNAL 0x00200000/* The internal lock is already held */ 141/* 142 * Internal state flags corresponding to lk_sharecount, and lk_waitcount 143 */ 144#define LK_SHARE_NONZERO 0x01000000 145#define LK_WAIT_NONZERO 0x02000000 146 147 148/* 149 * Lock return status. 150 * 151 * Successfully obtained locks return 0. Locks will always succeed 152 * unless one of the following is true: 153 * LK_FORCEUPGRADE is requested and some other process has already 154 * requested a lock upgrade (returns EBUSY). 155 * LK_WAIT is set and a sleep would be required (returns EBUSY). 156 * LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK). 157 * PCATCH is set in lock priority and a signal arrives (returns 158 * either EINTR or ERESTART if system calls is to be restarted). 159 * Non-null lock timeout and timeout expires (returns EWOULDBLOCK). 160 * A failed lock attempt always returns a non-zero error value. No lock 161 * is held after an error return (in particular, a failed LK_UPGRADE 162 * or LK_FORCEUPGRADE will have released its shared access lock). 163 */ 164 165/* 166 * Indicator that no process holds exclusive lock 167 */ 168#define LK_KERNPROC ((struct thread *)-2) 169#define LK_NOPROC ((struct thread *) -1) 170 171struct thread; 172 173void lockinit(struct lock *, int prio, const char *wmesg, 174 int timo, int flags); 175void lockdestroy(struct lock *); 176 177int _lockmgr(struct lock *, u_int flags, struct mtx *, char *file, 178 int line); 179void _lockmgr_disown(struct lock *, const char *, int); 180void lockmgr_printinfo(struct lock *); 181int lockstatus(struct lock *, struct thread *); 182int lockwaiters(struct lock *); 183 184#define lockmgr(lock, flags, mtx) \ 185 _lockmgr((lock), (flags), (mtx), LOCK_FILE, LOCK_LINE) 186#define lockmgr_disown(lock) \ 187 _lockmgr_disown((lock), LOCK_FILE, LOCK_LINE) 188#define lockmgr_recursed(lkp) \ 189 ((lkp)->lk_exclusivecount > 1) 190#ifdef DDB 191int lockmgr_chain(struct thread *td, struct thread **ownerp); 192#endif 193 194#endif /* !_SYS_LOCKMGR_H_ */ 195